A wall has a permanence to it that spans across Administrations.
Ever notice, say, a car repair shop where they have an 8 foot wall topped by razor wire? They build those because it reduces theft. Walls work, otherwise they wouldn't be built so often by property owners (both private and public).
Because no one along a 3145 km border would ever dig under the fence/wall, or cut a hole through it?
Belief in the effectiveness of a border barrier in stopping border crossers depends on never having looked at the problem in any depth. Pointing to the effectiveness of the East German border barrier as 'proof' of effectiveness simply highlights the ignorance of the advocates.
Here are some issues with this scheme.
The East German border was only 40% of this length, but required 47,000 border guards (there are only 20,000 border patrol agents), and it still depended on its effectiveness on a "shoot to kill on sight" policy, the use of land mines, and automatic firing weapons. Without the automatic use of deadly force the border would have remained quite leaky. U.S. law does not permit the use of death-traps or assassination by law enforcement.
Any such border barrier is only as strong as its most vulnerable point. Border crossers, and the coyotes who make money off of them, will be scouting the entire length looking for the spots where circumvention is easiest, and channel the traffic flow through that point, shifting to other points as needed as resources are thrown into the breech to close it. This is similar to U.S. efforts to block drug smuggling, which has never been effective since new holes are opened faster than old ones are closed - cocaine prices are currently at historic lows.
A substantial stretch of the US-Mexico border is through extremely rugged, remote terrain (which is why the border runs there) where it would be extremely difficult to build a fence or to patrol one. This extremely rugged terrain however is not impenetrable to motivated border crossers however, the rugged terrain provides cover in fact. No part of the East German border was as remote and rugged as this.
The desire by right-wingers to emulate the practices of Communist states is puzzling.